Precise Diagnosis And Treatment Of Pancreatic Ductal Adenocarcinoma Based On Multimodal Magnetic Resonance/Magnetic Particle/Near Infrared Optical Imaging

Objective:Pancreatic cancer is a highly malignant tumor of the digestive system.The five-year survival rate of pancreatic cancer is only about 11%,which is the lowest among all cancers and seriously threatens human health.Pathologically,pancreatic ductal adenocarcinoma(PDAC)accounts for over 90%of pancreatic cancer.The tumor microenvironment(TME)of PD AC,which is composed of fibrotic stroma,immune cells,and tumor neovessels,is characterized by multiple types of cells and molecules,spatial-temporal heterogeneity,and complicated interaction mechanisms.These TME features make the current diagnosis and treatment of PDAC faced with several challenges:(1)The development of PDAC involves the specific expressions of key molecules.However,the clinical contrast agents lack specific targeting ability to these key PDAC molecules,preventing the precise imaging of PDAC.(2)The highly immunosuppressive TME of PDAC,which is characterized by highly stromal fibrosis,a dearth of T lymphocyte infiltration and hypoxic environment,leads to the poor response to immunotherapy in PDAC.(3)The PDAC therapeutic approaches usually involve the TME remodeling including the fibrosis modulation,which is the key factor in therapeutic efficacy evaluation.However,the current evaluation criteria using computed tomography(CT)and magnetic resonance imaging(MRI)is based on the morphologic changes of PDAC,which cannot accurately reflect the TME fibrotic response during chemotherapy.Therefore,based on MRI,magnetic particle imaging(MPI),and near-infrared fluorescence(NIRF)multimodal imaging,this study intends to focus on the features of PDAC and its TME and carry out the PDAC diagnosis and treatment studies,including the precise molecular imaging,integrated immunotherapy,and accurate therapeutic efficacy assessment.Material and methods:In the section of precise molecular imaging,immunohistochemistry(IHC)staining,Western blot(WB)and flow cytometry were used to verify the specific expression of Plectin-1 in PDAC.PTP-Fe3O4-IRDye800CW targeted probe was prepared and injected intratumorally on subcutaneous and orthotopic animal models,respectively.MRI/MPI/NIRF multimodal imaging was performed in vivo,followed by pathologic staining of tumors and major organs to further verify the imaging results.In the section of integrated immunotherapy,new immunoactive peptide and photosensitive molecule co-assembled hydrogel(BV/TP5 hydrogel)was designed and injected intratumorally of PDAC model for photothermal immunotherapy.MRI and bioluminescence imaging were used to monitor the size and signals of tumor.Immunohistochemical/immunofluorescence staining and flow cytometry were used to explore the mechanism of immune regulation and hypoxic regulation.In the section of accurate therapeutic efficacy assessment,the imaging molecular probe ZD2-Gd-DOTA-Cy7 targeting specific molecule of TME fibrosis,extradomain B fibronectin(EDB-FN),was developed.MRI/NIRF imaging was performed after intravenous injection of the targeted imaging probe on subcutaneous and orthotopic models,and the in vivo imaging results were verified by immunofluorescence and pathological analysis.The ZD2-Gd-DOTA-Cy7 imaging probe was further injected intravenously on subcutaneous models treated with Albumin-bound paclitaxel and Gemcitabine(AG)chemotherapy or saline.Fibrotic changes before and after chemotherapy were quantitatively analyzed by MRI/NIRF imaging.Tumor volume was monitored,and therapeutic efficacy was verified by pathological analysis.Results:(1)Precise imaging of PDAC via MRI/MPI/NIRF imaging based on Plectin-1targeted molecular probe:Based on the high expression of Plectin-1 by PDAC and the complementary advantages of multiple imaging modalities,we constructed the PTPFe3O4-IRDye800CW imaging probe,which diffused and retained in PDAC tissue for a long time,and provided more significant signal enhancement for the tumor area.The optimal timepoint of imaging was post-injection of 2 day.MPI,a novel molecular imaging technology,integrated with NIRF and MRI could provide sensitive and high tissue resolution imaging.Plectin-1 targeted MRI/MPI/NIRF multimodal imaging provides a novel method for precise imaging detection of PDAC.(2)NIR photothermal immunotherapy of PDAC with the immunoactive peptidephotosensitive molecule co-assembled hydrogel monitored by MRI/optical imaging:Aiming at the highly immunosuppressive TME of PDAC,the developed injectable BV/TP5 hydrogel showed good biocompatibility and biosafety.Under the dual-modalilty monitoring of MRI and bioluminescence imaging(BLI),BV/TP5 hydrogel ablated tumor tissues by rapid local photothermal therapy in situ,relieving hypoxia,activating the immune microenvironment,and the systemic immune regulation of TP5.Combination of the photothermal therapy with immunotherapy showed synergistic effects on significantly and effectively inhibiting the progression and metastasis of PD AC,and provided promising treatment strategies for the immune "cold" tumor.(3)Quantitative monitoring of fibrotic response to PDAC chemotherapy via MRI/NIRF imaging with the EDB-FN-targeted molecular probe:Focusing on the PDAC TME fibrosis,an important indicator of AG chemotherapy efficacy,we prepared the ZD2-Gd-DOTA-Cy7 dual-modality imaging probe.Compared with Gd-DOTA,ZD2Gd-DOTA-Cy7 probe achieved accurate MRI/NIRF imaging of PDAC fibrosis at the Gd concentration of 0.05 mmol/kg,which was only 50%of the clinical dose of contrast agent Gd-DOTA.The optimal timepoint of imaging was post-injection of 30min.ZD2-GdDOTA-Cy7 probe realized the non-invasive detection and quantitative evaluation of AG chemotherapy in PDAC from morphological to molecular level.Besides the traditional Response Evaluation Criteria In Solid Tumors,the MRI/NIRF imaging with the ZD2-GdDOTA-Cy7 probe provides a novel method to quantitatively visualize the changes of fibrotic components in the accurate PDAC chemotherapy efficacy evaluation.Conclusion:Aiming at the characteristics of PDAC and its TME,this study realized the precise molecular imaging,NIR photothermal immunotherapy,and quantitative monitoring of fibrotic response to PDAC chemotherapy based on the strategy of MRI/MPI/NIRF multimodal imaging,which provided a novel approach for imaging diagnosis,a promising tool for therapeutic intervention,and a new method for therapeutic efficacy evaluation in PDAC.